1. Field of the Invention
The present invention is directed to a computer tomography apparatus, and in particular to a cooling system for such an apparatus.
2. Description of the Prior Art
Computer tomography devices are known in the art consisting of a stationary apparatus part in which a live ring is rotatably seated, the live ring carrying heat generating components such as an x-ray source and a radiation detector at opposite sides of an opening in which an examination subject is received. For cooling the apparatus, an annular channel is provided which is limited by the stationary apparatus part and the live ring, the channel having at least one inlet and at least one outlet for a gaseous coolant. A conduit, also containing a coolant, is connected to the live ring and has various portions disposed in proximity to the heat generating components so as to carry heat away from those components, and another portion disposed in the annular channel so that the coolant in the channel carries away the heat from the conduit.
Such a computer tomography apparatus is described in published European Application No. 0 182 040, corresponding to U.S. Pat. No. 4,651,338. In this apparatus, the conduit forms a closed cooling circulation loop on the live ring, the heat from the heat generating components, particularly from the x-ray tube, being transferred to the coolant in the conduit. This conduit coolant flows through the portion of the conduit in the annular channel of the live ring, and the heat from the coolant is emitted into the ambient air within the channel, which functions as a gaseous coolant. The air within the channel flows through the channel in a direction from the channel inlet to the channel outlet. Heat elimination from the live ring to the outside of the device is thereby achieved.
A disadvantage of this apparatus, however, is that an air draft, which is undesireable for hygienic reasons, arises in the room in which the tomography apparatus is disposed. In theory, such an air draft could be avoided by supplying the air flowing in the annular channel from the exterior of the room, and eliminating the heat-containing air to the exterior by respective lines connected to the channel inlet and outlet. This would require, however, considerable structural modifications to the room in which the apparatus is disposed, and such lines are additionally undesireable because of the space which they occupy.